Device for testing the residual power capacity of a battery supplying a glow discharge tube or the like



3,063,004 F A BATTERY R. VIC

UAL POWER CAPACITY O E OR THE LIKE SUPPLYING A GLOW DISCHARGE TUB Filed May 26, 1959 Nov. 6, 1962 DEVICE FOR TESTING THE RESID United States Pa fl 3,063,004 1' DEVICE FOR TESTING THE RESIDUAL POWER CAPACITY OF A BATTERY SUPPLYIN G A GLOW DISCHARGE TUBE OR THE LIKE Raymond Vic, La Celle St. Cloud, France, assignor to. The Compagnie Industrieile des Piles Electriques Cipel, Neuilly-sur-Seine, France, a company of France Filed May 26,1959, Ser. No. 816,002

2 Claims. (Cl. 324--29.5)

This invention relates to glow discharge tube installations utilizing a battery type generator as the power source supplying energy to one or more glow tubes by way of suitable oscillator and transformer means. Such installations have important uses, e.g. in rail-way signalling equipment, but have been subject to the following drawback. In contrast to the more conventional resistance lamp,.a glow lamp or'tu-be will continue operating satisfactorily even after the voltage supplied to it from the generator has decreased considerably, a large reduction in the available voltage-bringingabout only a very small drop in the brightness of the tube. It is only when the voltage developed byfthe generator has decreased below a certain threshold 'value that'th'e'glow' tube i'se'x'tinguished. Because of this, there is no convenient means of ascertaining in installations of the type described, when to change the supply "battery in order to avert a sudden and unexpected extinction of the glow lamp or lamps. This is a very serious drawback e.g. in connection with a railway signal light.

It is an object of this invention to provide, in such installations, a means of conveniently checking at any time whether the power source is still capable of adequate service, and of doing so during the operation of the system, and without disabling the latter.

As will be apparent from the ensuing description, the invention makes it possible to determine by an extremely simple operation such as the actuation of a push-button switch, if the residual power capacity of the battery is sufficient to ensure proper operation until the next test (assuming such tests are performed at regular predetermined intervals). The glow lamp remains illuminated during the test, if he condiionnhetaoinshsdlucmfwyphshrdlu ing the test, if the condition of the battery is such as to ensure continued operation of the glow discharge lamp until the next scheduled test, whereas, the lamp or tube is temporarily extinguished if the battery is spent to an extent that it will not ensure proper service until the next test and hence requires replacement.

According to the invention, means are provided for momentarily inserting into the supply circuit for the glow lamp or lamps a suitable voltage drop. This voltage drop, as represented e.g.; by a set of resistances, is so predetermined that the remaining operating time of the battery after the test remains greater than the time interval separating two successive tests in cases where the tests are carried out at predetermined intervals as just stated.

According to another feature of the invention, allowance is made for the fact that the voltage available across a battery decreases substantially with the surrounding temperature. Thus, if the ambient temperature is relatively low at the time the test is performed, the test may cause the lamp to be put out thereby indicating the need to replace the battery, whereas actually the battery may still be in a condition to furnish suflicient energy for the requisite period of time. Accordingly, the invention contemplates automatically varying the value of the voltage drop momentarily introduced into the lamp supply circuit with temperature, as by providing a resistance having a negative temperature coetficient or a thermistor connected to the battery.

3,003,004 Patented Nov. 6, 1962 The invention will be better understoodfrom'the ensuing description which is illustrative but is not restrictive." Inthe drawings: I FIG; 1 is a wiring diagram of an installation equipped with atesting device'embodying the invention; i FIG. 2 illustrates part of the installation of" FIG. 1 showing the condition of the circuitry during'normal op eration thereby; and

FIG. 3 is a view similar to that of FIG. 2 showing the same part of the circuit, but illustrating the conditions during a testing operatic The installation shown in FIG. 1 comprises a battery 1 supplying a glow discharge tube 9 by way of a supply circuit comprising a transistor oscillator 2 and a trans former 4. The secondary 8 of the transformer is connected across the glow tube 9. The primary of the transformer isin two parts 3 and 3', each having one end connected to a battery terminal'line 11 or 13. The upper part 3 of the primary has its said one end further'com nectedto the base ofthe transistor by way of a resistance 6 and its other end connected to another electrode of the transistor, while the lower part 3' of theprimary has its said one end connected to the remaining electrode of the transistor and its other end connected to .the base by way of resistance "Due to the resistances 5 and 6, theiran sistor operates as a blocking oscillator. A condenser 7 across the supply lines 11 and 13 serves to smooth out the output of the oscillator. The battery 1 may comprise a set of cells sold by the applicants as Type AD 535.

A low resistance 10 is connected in series in the supply line 11 and has a very low value, say 20 ohms. This resistance is normally short-circuited across its ends A and B by means of a switch '12, when the latter is in the position shown in full lines in FIG. 1. The switch 12 is preferably in the form of a manually operable push-button switch.

When the switch 12 is moved to the position 12 shown in dotted lines, the resistance 10 is placed in the supply circuit for the part 3' of the transformer primary, and simultaneously a connection 14 is established from point B to the supply line 13 by way of two series resistances 15 and 16. Resistance 16 is a resistance having a negative temperature coefficient i.e. a thermistor. Its characteristics may be such that the resistance is 60 ohms at 20 C., 30 ohms at 0 and 4 ohms at +50. These values of course are indicative only.

The resistance 15 may be 5 ohms in value and its function is to set a limit to the conductivity of the thermistor 16 at high temperatures.

In normal service conditions, with switch 12 in the position shown in full-lines, the circuit connections are established as shown in FIG. 2, that is, resistance 10 is shorted and the transformer primary is supplied from the battery as if the resistances 10, 15 and 16 were absent. To perform a test the switch 12 is displaced to its dotted-line position 12' (as by pressing a button) whereupon the resulting circuit connections are as shown in 'FIG. 3. The transformer primary is then supplied from the battery by way of a voltage divider comprising the resistances 10, 15 and 16, with the voltage being taken across the resistances 1S and 16.

The three resistances are so predetermined that the voltage drop thus introduced on movement of the switch to position 12' reduces the voltage available for the lamp 9 across the secondary 8 of the transformer to the critical extinguishing level, with the battery cells operating under 4 volts at ordinary temperature. Under these conditions one will be sure of the correct subsequent operation of the lamp for approximately another 50 hours assuming the tests are carried out at regular 12 hour intervals as is gen er-ally the case in connection with railway signal systems.

If the surrounding temperature drops, the voltage put out by the battery drops correspondingly, but since the 3 resistance of thermistor 15 increases, matters can be so arranged that the voltage drop across the series resistances 15-16, during the test remains approximately constant and independent of temperature. In practice it has been found possible to use the system described successfully over a temperature range of from 20 C. to 50 C., with the voltage developed by the battery varying from about 2.4 volts at -20 C. to 4.4 volts at 50.

It will be evident that various modifications may be made within'the scope of the invention. For example, the temperature compensating resistance 16 may well be dispensed with in case the installation is not to be subjected to wide temperature variations. The oscillator system used has been shown as a transistor, but may assume any other desired form, including that of thermionic tubes, mechanical vibrators or the like. The means for introducing the voltage drop may likewise differ from the resistance network shown.

What I claim is:

1. A device for periodically testing the state of charge of a battery which is regularly employed for energizing at least one glow discharge tube by way of a supply circuit including oscillator means and transformer means; said device comprising additional load defining means including a resistance having a negative temperature coefiicient, and means for introducing said load defining means into the supply circuit during testing of the state of charge of the battery, said load defining means being dimensioned 4 so that, with said load defining means introduced into the supply circuit, the glow discharge tube continues to be illuminated only if the state of charge of the battery is such as to ensure continued illumination of the tube by the battery for a predetermined duration after the test.

2 A device as in claim 1, wherein said means for introducing the load defining means into the supply circuit includes switch means having normally closed contacts and normallyopencontacts, said load defining means further includes an additional resistance, the first mentioned resistance being connected in parallel with the oscillator means and transformer means upon closing of said normally open contacts and said additional resistance being connected in series with the oscillator means and transformer means upon closing of the normally open contacts, and said normally closed contacts forming a short circuit around said additional resistance.

References Cited in the file of this patent UNITED STATES PATENTS 896,300 Jarvis Aug. 18, 1908 2,887,592 Stout et al May 19, 1959 FOREIGN PATENTS 207,578 Great Britain Nov. 30, 1923 391,690 Germany Mar. 14, 1924 438,407 Great Britain Nov. 15, 1935 924,329 France Mar. 3, 1947 

